This invention relates generally to duplicating machines and, more particularly, to an ink or moisture feeding system including an improved ink or moisture pickup roller.
Printing machines, such as rotary offset lithographic duplicating machines, rotary printing presses, or the like normally include a printing couple which comprises a number of cylinders and/or rollers for supplying ink from a reservoir. In offset lithographic machines, moisture also is supplied from a reservoir. A fountain for the ink or moisture is provided for feeding ink, for instance, to the various rollers of the printing couple which transfers images to copy sheets.
Conventional ink fountain assemblies normally take the form of a fountain trough defined by an elongated blade extending along one side and an ink fountain roller extending along the opposite side of the trough. The ink fountain roller transfers the ink to a pickup roller and other rollers of the printing couple to smooth out the ink film and carry it to a plate or printing cylinder which applies the ink in a desired pattern to the copy sheets or paper. The ink fountain blade is adjustable by a plurality of thumb screws to vary the gap between an edge of the blade and the ink fountain roller in order to maintain consistency in the amount of ink applied to the roller along the length of the roller.
The pickup roller conventionally comprises either a continuous contact roller or a ductor roller which oscillates back and forth to intermittently pick up ink from the fountain roller. It can be understood that the better the pickup roller is able to supply an even and uniform flow of ink, the less need there will be for spreading out and smoothing the ink film as it is carried to the plate or printing cylinder. Problems constantly are encountered in achieving such an even and uniform flow of ink to the printing couple. With continuous pickup rollers, having smooth surfaces, the thickness of the ink film on the fountain roller must be quite thin. Obviously, with such a thin film, there is a very small range to work with in adjusting the thickness of the film which is transferred by the pickup roller.
With conventional ductor rollers, problems constantly are encountered by shadows caused by ductor roller skidding and bouncing. Ductor rollers also require complicated and expensive ducting mechanisms.
In either a continuous contact roller system or a ductor roller system, it is widely known that a smooth surfaced pickup roller does not feed an even flow of ink to the inking system. A pattern of irregular ink blotches forms on a smooth surfaced pickup roller so that ink is not uniformly delivered for any given area of thumb screw adjustment and fountain blade setting.
Attempts have been made to provide a pickup roller with a non-smooth surface to better supply an even and uniform flow of ink to the inking system. For instance, the entire surface of the pickup roller has been formed with a pattern of projections, such as tiny pointed pyramids as shown in U.S. Pat. No. 2,213,419, issued Sept. 3, 1940, to Taylor. Not only is such a roller extremely expensive to manufacture, but the myriad of grooves and projections do not provide a sufficiently consistent supply of ink which, thereby, inhibits the control necessary for precision machines.
Another example of providing a non-smooth surface on the pickup roller is shown in U.S. Pat. No. 3,098,437, issued July 23, 1963, to Tyma, Jr., et al. This patent shows one of various attempts to provide a helical pattern of grooves which define rounded ridges and valleys helically around the surface of the pickup roller. A major problem with such helical configurations is that the pattern of ridges or grooves act as a screw pump. Consequently, the ink tends to move from one ridge to the next ridge, rather than providing a continuous flow of ink from the fountain roller to the transfer roller system.
This invention is directed to solving the above problems by providing a new and improved pickup roller for ink and/or moisture feeding systems.